Restoration Project #33 - Precision Model 612 Tube Tester - Part 1

I got some vacuum tube based projects in my pipeline and might get more of those over time... so I decided to go for a "tube tester", which were quite common in the days of tubes. There are different categories of those: simple short and heater testers that might include a "yes/no" light indicator to show that they are doing something; on the other end of the spectrum are complete classification devices that can accurately measure tubes. Neither of which makes sense for my intended purpose. I want a bit more than a pure yes/no result but I don't need a full lab setup either. So the third category in the middle was my choice: an emission tester. These heat up the tube and put a current through it, connected to an analog readout to show how good or bad the tube is, compared to its "should" current.

As a complete random coincidence, I found a Prcision Instruments - or Precision Apparatus? I've seen both names on plates and documents - model 612; It is a rather versatile device in this category and it fits the Precision VTVM that I restored last year perfectly! Exact same case! Down to the two random holes in mine, which are used in this one, so now things make sense!

It was in similar neglected condition when I got it and I started the restoration process with some cleaning... But oh, did I underestimate the required work involved... This is part one of two, so be sure to check in again in about two weeks, when the conclusion will be presented!


0:00 Intro - Presentation
1:02 Main Component Disassembly, Case
2:20 Carry Handle, Rust Remover Issues
3:15 New Plywood Cover Plate / Case Sanding
4:00 Wood Treatment / Carry Handle Pins / Hardware Remount
5:15 Accessories Compartment Lining / Badge
6:21 Tube Sockets and Adapter / Adapter Paint and Assembly
8:01 Device Disassembly Start / Tube "Database" Overview
9:05 Desoldering Tube Sockets
10:13 Separatng Guts and Front Panel
10:50 Desoldering Transformer
12:00 Transformer Overview
12:55 Removing Primary Winding
13:40 Unwinding / Be Kind, Rewind!
15:40 New Coil Done! / Testing!
16:40 Panel Cleaning / Meter Disassembly
17:50 Oxydation / Characterization / Movement Disassembly
19:04 Rust and Surface Treatment
20:25 To be continued...


Music:
My Train's A Comin'
Unicorn Heads
(YouTube Audio Library)

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